Taut suspension system



y 1955 H. J. LOVEGROVE 3,

TAU'I SUSPENSION SYSTEM Filed Oct. 15, 1963 Henry dose 06 [away/aveINVENTOR.

ATTORNEY United States Patent 3,193,896 TAUT SUSPENSION SYSTEM HenryJoseph Lovegrove, Hadley Wood, Barnet, England, assignor to WestonInstruments, Inc., a corporationof Texas Filed Oct. 15, 1963, Ser. No.316,321 Claims priority, application Great Britain, Oct. 16, 1962,39,153/ 62 t 4 Claims. (Cl. 24-126) This invention relates to suspensionarrangements for the moving element of an instrument such as the movingcoil of an electrical measuring instrument and is more particularlyconcerned with arrangements of the taut suspension type in which finewires, strips or the like extend under tension from opposite points ofthe moving element to fixed supports on the stationary part of theinstrument.

In suspension arrangements of the known type, difiiculties arise inanchoring the ends of the ligaments which constitute the suspensionmeans, especially when these also form the means for conducting currentto the moving element. Soldering of the ligament to suitable anchoragepoints is a conventional method of securing, but this involves the riskof altering the physical characteristics of the ligament owing totheheating which necessarily "ice ment along the pin either during thesecuring operation or subsequently. In addition, the clamping operationmust not damage the ligament wire. Such clamping may be achieved byapplying a suitable pressure force P in a. direction substantiallyperpendicular to the pin axis.

One practical embodiment is shown in FIG. 2 and comprises a cylinder 12,conveniently of metal, having a occurs; in addition it is difiicult toperform, particularly with the very fine wires currently employed,without disturbing the previously adjusted tension applied to theligament.

An object of the present invention is the provision of 'member extendstangentially from the pin surface and such wire or strip is secured bypressure applied in a direction substantially perpendicular to the pinaxis to clamp the ligament to the surface of the pin at a position atleast displaced from the tangent point. Such clamping pressure ispreferably applied through a clamping pad which, while free to movealong the direction of pressure application, is restrained from possiblemovement in directions perpendicular to such pressure direction.

In order that the nature of the invention may be more readily understooda number of embodiments will now be briefly described by way ofillustrative examples and with reference to the accompanying drawingwherein:

FIG. 1 shows the basic suspension arrangement in accordance with theinvention. FIG. 2 is a perspective view of a preferred embodimentincorporating the suspension arrangement shown in FIG. 1. FIGS. 3 and 4are modifications of the embodiment shown in FIG. 2. FIG. 5 is aperspective view of a simplified suspension system. FIG. 6 is a partialview in section of a modification of the embodiment shown in FIG. 5.

Referring first to FIG. 1, the suspension arrangement is basically onein which the wire-shaped suspension ligament 10 is held over acylindrical roll pin 11 so that the part 10a of the ligament whichextends in tension as the suspension link does so tangentially withrespect to the pin surface. This ligament is required to be heldsecurely so that it is free to pivot or roll on the pin withoutinterference while being constrained against axial displacecoaxial bore13. A pair of opposed holes 14 near one end receive, in tight fittingengagement, the cylindrical roll pin 11 while towards the opposite endof the cylinder 12 a second pair of holes 15 receives a tapered pin 16.An axially directed slot 17, lying in a plane substantiallyperpendicular to the roll pin 11, is provided in the cylinder wall. Slot17 may, as shown, also pass through one of the holes 15. The axis of theholes 15 conveniently passes through the axis of the cylinder 12 but theaxis of the holes 14 is ofiset from the axis of the cylinder 12 by anamount equal to the radius of the roll pin 11 plus half the diameter orthickness of the suspension ligament. A pressure pad 18, in the form ofa thick disc of slightly smaller diameter than the bore 13, is disposedin such bore between the tapered pin 16 and the suspension ligament 10lying around the roll pin 11.

In the operation of effecting clamping, the roll pin 11 is firstinserted. The suspension ligament 10 is then passed up the bore 13 ofthe cylinder 12 to rest against the side of the roll pin in a locationwhere it lies on the axis of the cylinder 12. The projecting upper endis then bent over the roll pin so that it passes out through the centerof the slot 17. At this time the ligament may be tensioned to therequired degree. The pressure pad 18 is then inserted through the top ofthe bore 13 to rest by its fiat undersurface upon the suspensionligament lying upon the upper surface of the roll pin 11. The taperedpin 16 is then inserted to overlie the pad 18 and thereafter pushedhome, e.g. by means of pliers or other suitable tool to force the padinto clamping engagement with the ligament lying on the roll pin.

While the preferred arrangement is as shown in FIG. 2 where the taperedpin is at right angles to the roll pin, this is not essential and theangle between the respective axes of the pins may be of any convenientvalue. FIG. 3 illustrates an alternative construction in which the twopins are parallel with one another. This construction is of simplifiedform, the hollow and slotted cylinder 12 of FIG. 1 being replaced by asolid cylinder 20 provided with a wide milled slot 21 therein. Thepressure pad 22 is now rectangular and is a neat sliding fit within theslot. FIG. 4 shows yet another alternative in which the main body 24,replacing the parts 12 or 20 in the earlier embodiments, is ofrectangular section channel form made by folding a suitably shapedblank.

Other means for applying the clamping pressure upon the pressure pad maybe used. For example, in the form of construction shown in FIG. 2, theupper end of the bore 13 may be threaded for receiving a clamping grubscrew bearing by its lower end upon the pad disc 18.

The materials employed, particularly for the roll pin 11 and thepressure pad 18 or 22, are chosen to avoid oxidation and destructive ordamaging effects upon the ligament. Stainless steel has been foundsuitable for the roll pin 11 and silver for the pressure pad.

The constructions already described may be used at either or both endsof each suspension link but, since one end attachment can nearly alwaysbe pre-assembled, a simpler embodiment can often be used for that end,usually the one secured to the moving element, such as the moving coilof an electrical measuring instrument. Such further embodiment is shownin FIG. 5 and comprises a base pedestal 26 provided with a securing footpiece 27. The pedestal is formed with a transverse slot 28 so positionedthat one side wall is in a plane which is displaced away from thedesired ax s line'of the suspension liga- Q ment by an amount equal tohalf the ligament thickness. 7

This slot is 'of'such width that it provides an interference f fit for aroll pin 11. y The bottom of the slot 28 isof the 1 same radius as thepin, on that sideof thje slot 28 adjaei cent the axis line of thesuspension, thepedestalispro with the centerjof the slot 29 and with thesuspension link part 10a projectingin the directioniof such slot 29. Theroll pin 11 is'thensforced downwardly into thesiot 28 right to thebottom-thereof. Asa result, the ligament '10 is clamped for 90 of thecircumference of the pin 11 I i V H The part: iltla of the ligament isthen broughtupvthrough-the slot'zfir r 1 {2'0 between suchi'pin and thebottom of thefslot.

for' attachm'ent by its other end to the opposing anchorage point. i

In another alternatiy eg as shown in FIG."6, a roll, 11 which is smallerindiameter than the slot '28 may be 7 'used, thisrpin being followed bya wedge pin 11a which. j '1 isan interferencefit in theslot. A groove-1-1b:is suit.- ably provided in the Wedge pin 114 at its center regionto avoid any contact therewith by the upwardlyextending part ltla of theligament. V r i 7 While I have illustrated of preferred embodiments ofmy invention, it will be'apparent to those skilled in 'the art thatchangesma'y be made in the 'form of theapparatus without departing fromthe spirit of my inventionas set forth in the ap'- pended claims. r, 1'What is claimed is: V 1 e a v stantially perpendicular.

defining a coaxial bore and a coaxial slot extending from'saidboreto'the outer wall of said cylinder, said bore and said slot allowing'forthe free passage of said first and second endsof said ligament, adisk-shaped pad, and I a 'means including a wedge pinmechanicallycoupled to V f said base member for pressing said-pad against at leastiaportion of said ligament which isincontact with'said curved surface. I 2The suspension mechanism or claim 1 wherein the 'axesiofsaidwedge pinand of said elongated pina're sub- 3. A taut suspension mechanismcomprising:

T V an'elongatedipin havinga curved surface,

ancldescribed thebest a flexible elongated ligament having a first andasecg ond end,v atrleast one'of said ends being in tension, saidligament being supported-by'said pin in a plane 1 substantiallyperpendicular to the-longitudinal axis 7 'Y of said pinwhereby saidligament embraces atleast:

a portion of said curved surface; c 1" a base memberrin'the form of acylinder-for supporting.

said pin at the extremities thereof; said base member 5 BOBBY;- R, GAY,Examiner.

a flexible'elongated ligament having a first and a sec- 0nd end,;atleast one of said ends being in tension, sai-d'ligamentbeing supportedby said'pin'in a plane substantially perpendicular to the. longitudinalaxis ofsaid pinwhereby saiclligament embraces at least ;a portion ofsaid curved surface, U shaped base" memberi-for' supporting said pin atthe extremities thereof, thereby allowing for the free passage of said;first and second ends of said ligament Y I f a rectangularly sha pedpad, and I 7 means including: awedge pin mechanically coupled "to saidbase member for pressing said pad against at least a portion of said'ligamentwhich'is in contactwith said curved'surface: i 4. Thesuspension mechanism of claim'3 wherein the axesfof said wedgepinandt'of said elongated pin lie in substantially parallel planes.

Retei'ences Cited byfthe Examiner FUNITED, STATES PATENTS- e VVFOREIVGNPATEVNTSV I g 662,201 z/51' .GreatBritain'.

DQNLEY I. STOCKING; rimar Examiner.

1. A TAUT SUSPENSION MECHANISM COMPRISING: AN ELONGATED PIN HAVING ACURVED SURFACE, A FLEXIBLE ELONGATED LIGAMENT HAVING A FIRST AND ASECOND END, AT LEAST ONE OF SAID ENDS BEING IN TENSION, SAID LIGAMENTBEING SUPPORTED BY SAID PIN IN A PLANE SUBSTANTIALLY PERPENDICULAR TOTHE LONGITUDINAL AXIS OF SAID PIN WHEREBY SAID LIGAMENT EMBRACES ATLEAST A PORTION OF SAID CURVED SURFACE, A BASE MEMBER IN THE FORM OF ACYLINDER FOR SUPPORTING SAID PIN AT THE EXTERMITIES THEREOF, SAID BASEMEMBER DEFINING A COAXIAL BORE AND A COAXIAL SLOT EXTENDING FROM SAIDBORE TO THE OUTER WALL OF SAID CYLINDER, SAID BORE AND SAID SLOTALLOWING FOR THE FREE PASSAGE OF SAID FIRST AND SECOND ENDS OF SAIDLIGAMENT, A DISK-SHAPED PAD, AND MEANS INCLUDING A WEDGE PINMECHANICALLY COUPLED TO SAID BASE MEMBER FOR PRESSING SAID PAD AGAINSTAT LEAST A PORTION OF SAID LIGAMENT WHICH IS IN CONTACT WITH SAID CURVEDSURFACE.